This invention relates to the cleaning of storage tanks used in petrochemical plants or oil refineries, and more particularly, to systems for removing waste materials which accumulate over time in such tanks.
In the petroleum refining and petrochemical chemical industries large storage tanks are in common usage. Various processes cause waste materials, both solid and liquid, to be generated along with the desired products. The accumulation of such waste materials, or sludge, can occur in these large storage tanks. It is not uncommon to have several feet of such sludge in the bottom of a single such large storage tank. The sludge usually contains a fairly high percentage of hydrocarbon which can be recycled if separated from the solid irreducible waste which may comprise catalyst fines, rust or other particulate matter developed in a particular chemical process.
In the prior an heated diluent such as diesel fuel or light crude oil or water is directed by a central manifold or by hand held hose inside a storage tank against the sludge therein. This can convert the sludge into a pumpable slurry which is then pumped from the tank and further treated to separate out reusable hydrocarbons and recycle the diluent while discarding the solid waste. It was also proposed in U.S. Pat. No. 4,817,653 to use a waste washing robot operated by a human operator positioned inside the tank to spray water under pressure against tank residue to cause dislodgment of the sludge or other waste.
In practicing such cleaning techniques it has heretofore been necessary to have an observer in line of sight of the point of application of the water or heated diluent order to control this portion of the process. This has necessitated humans inside the tank being cleaned. Workers can thus be exposed to H.sub.2 S, benzene or other potentially poisonous or highly volatile atmospheres. In the present invention this potentially dangerous exposure is eliminated through the use of robotic, remote controlled, devices operable from a safe distance from the tank. The extremely labor intensive, dangerous, work by humans inside of tanks being cleaned is virtually eliminated by the system of the present invention.